Removal of Perchlorate from Contaminated Waters Using Surfactant‐Modified Zeolite

Abstract

Abstract We investigated the potential of using surfactant (hexadecyltrimethylammonium)‐modified zeolite (SMZ) as an inexpensive sorbent for removing perchlorate (ClO 4 − ) from contaminated waters in the presence of competing anions. In batch systems, the presence of 10 m M OH − (i.e., pH 12), CO 3 2− , Cl − , or SO 4 2− had little effect on the sorption of ClO 4 − by SMZ, indicating that the sorption of ClO 4 − by SMZ was very selective. The presence of 10 m M NO 3 − , however, reduced the sorption of ClO 4 − at low initial concentrations. The maximum sorption capacity for ClO 4 − by the SMZ remained relatively constant (40–47 mmol kg −1 ), in the absence or presence of the competing ions. In flow‐through systems, ClO 4 − broke through the SMZ columns much later than other anions present in an artificial ground water. The affinity of the anions for SMZ followed the sequence of ClO 4 − > > NO 3 − > SO 4 2− > Cl − Perchlorate loading under dynamic flow‐through conditions was 34 mmol kg −1 , somewhat less than the maximum loading of 40 to 47 mmol kg −1 determined by the batch method. Less than 1% of previously sorbed ClO 4 − was leached out by ultra‐pure water, by extraction fluid #1 of the standard toxicity characteristic leaching procedure (TCLP), or by a solution of 0.28 M Na 2 CO 3 /0.5 M NaOH. About 40% of the previously sorbed ClO 4 − was leached out from SMZ by a 0.5 M NO 3 − solution. The exchange of ClO 4 − with NO 3 − corroborated results of the batch tests where NO 3 − was shown to compete with ClO 4 − sorption.